The present application is based on Japanese priority application No.11-279943 filed on Sep. 30, 1999, the entire contents of which are hereby incorporated by reference.
The present invention generally relates to magnetic storage of information and more particularly to a magnetic disk device having an improved seek control.
In a magnetic disk device that stores information on a rotary magnetic disk, it is necessary for a magnetic head to scan over a surface of the rotary magnetic disk, when reading information from the rotary magnetic disk, until it reaches a specific cylinder or a target track on which the information to be read out is recorded. Such a scanning operation of the magnetic head is called a seek operation and the duration for the seek operation is called a seek time. The smaller the seek time, the higher the access speed of the magnetic disk device.
On the other hand, in the actual magnetic storage device, there arises a case in which the magnetic head, carried on a swing arm at a tip end thereof, may reach the target track with a timing offset from the nominal timing for the portion or sector of the target track (target sector) on which the information to be reproduced is recorded. In such a case, the magnetic head cannot reproduce the information immediately from the target sector but has to wait on that track for another turn of the magnetic disk until the target sector that carries the information to be read out comes right underneath the magnetic head. However, the existence of such a waiting time decreases the reading speed of the magnetic disk device.
FIG.1 is a diagram showing the construction of a magnetic disk device 1 called a hard disk device according to a related art.
Referring to FIG. 1, the magnetic disk device 1 includes a magnetic disk 14 accommodated in an enclosure 10 having a cover 12 and stores information on the magnetic disk 14 along concentric tracks or cylinders defined thereon. The magnetic disk 14 is mounted on a spindle motor 18 for rotation, and a floating magnetic head 16 scans over the surface of the magnetic disk 14. The magnetic head 16 is mounted at an end of a swing arm 24, wherein the arm 24 is connected to a voice coil motor 20 and the voice coil motor 20 actuates the arm 24 for the swinging motion. With the swinging motion of the arm 24 thus caused by the voice coil motor 20, the magnetic head 16 scans over the surface of the magnetic disk 14 generally in a radial direction thereof. Thereby, the magnetic head 16 is controlled so as to trace a desired track on the magnetic disk 14.
FIGS. 2A and 2B show the magnetic disk 14 respectively in a plan view and in a cross-sectional view.
Referring to FIG. 2A, it can be seen that there are a number of concentric tracks 30 formed on a magnetic recording surface 26 of the magnetic disk 14, wherein the magnetic recording surface 26 is formed on both sides of the magnetic disk 14. Each of the tracks is divided into a number of sectors 28, and the magnetic head 16 scans over the magnetic recording surface 26 so as to record or reproduce information on or from a selected target sector 28 of a selected target track 30.
As represented in the cross-sectional view of FIG. 2B, the magnetic head 16 includes an upper head 16(n) locating above the magnetic disk 14 and a lower head 16(nxe2x88x921) locating below the magnetic disk 14, wherein the upper and lower magnetic heads are floating from the respective, corresponding magnetic recording surfaces 26n and 26nxe2x88x921 by a thin air film. By actuating the arm 24, the magnetic head 16 performs a seek operation across the tracks 30 from a first track to a next track.
In the magnetic disk device 1 of FIG. 1, it should be noted that the magnetic disk 14 in fact includes a plurality of magnetic disks held on the spindle motor 18 coaxially, and the swing arm 24 in fact includes a number of swing arms driven by the voice coil motor 20 as a unitary body. Thereby, the swing arms 24, and hence the magnetic heads 16 held thereon, scan over the corresponding magnetic disks 14 simultaneously.
The concentric tracks 30 thus formed on the magnetic recording surfaces collectively constitute a cylinder. Thus, a track on the recording surface 26n and a corresponding track on the recording surface 26n+1 form together a cylinder.
FIG. 3 shows an example of the seek operation of the magnetic head 16 after the magnetic head 16 has reached a target track or a target cylinder HD(n).
Referring to FIG. 3, the magnetic head 16 assumes a state {circumflex over (1)} immediately after it reaches the target track HD(n), wherein it can be seen that the target sector or sectors, from which the information is to be read out, has or have already passed the position of the magnetic head 16.
Under such a situation, it has been practiced to hold the magnetic head 16 on the target track HD(n) until a situation {circumflex over (2)} occurs in which the magnetic disk 14 makes another turn and the target sector or sectors comes to the position ready for scanning by the magnetic head 16 on the track HD(n). However, such a conventional seek control process inevitably wastes time and increases the seek time, and hence the access time, of the magnetic storage device.
In the conventional seek control of magnetic heads, a problem similar to the one explained with reference to FIG. 3 can occur also when there occurred a switching of the magnetic head 16 from the first magnetic head 16(n) scanning the first recording surface 26n of the magnetic disk 14 to the second, different magnetic head 16(nxe2x88x921) scanning the second recording surface 26nxe2x88x921 of the magnetic disk 14 as represented in FIG. 2B.
Referring to FIG. 4, there occurs a switching of the magnetic head 16 from a first magnetic head such as the magnetic head 16(0) scanning a track HD(0) on a first recording surface of the magnetic disk 14 to a second magnetic head 16(2) scanning a track HD(2) of a second recording surface of the magnetic disk 14, with a timing such that the second magnetic head 16(1) starts scanning of the first sector 0 of the track HD(1) in response to the completion of scanning of the last sector n of the first track HD(0).
In order to achieve such a successive cross over of the magnetic heads and hence the tracks, there is provided a predetermined skew between the tracks HD(0) and HD(1), so that the sector 0 of the track HD(0) comes to the position ready for scanning by the second magnetic head when the switching over is completed from the first magnetic head 16(0) to the second magnetic head 16(1) as represented in FIG. 4 by a broken line.
Thus, as long as the skew thus set is appropriate, the first and second magnetic heads 16(0) and 16(1) constituting collectively the magnetic head 16 successively reproduce information from the sector n of the track HD(0) on the first recording surface and then from the sector 0 of the track HD(1) on the second recording surface.
In the case the actual skew between the magnetic tracks HD(0) and HD(1) is different from the predetermined skew as represented in FIG. 4 by a continuous line, on the other hand, the second magnetic head 16(1) fails to scan the heading part of the target sector 0 of the target track HD(1) or may even skip the target sector 0 entirely. Thereby, it has been necessary for the second magnetic head 16(1) to wait on the track HD(1) until the magnetic disk 14 makes a further turn and the heading part of the target sector 0 returns again.
Further, such a waiting status may occur also in the seek operation of the magnetic head 16 scanning over the magnetic recording surface in a radial direction of the magnetic disk 14 by way of driving of the voice coil motor 20 in search of a target track. It should be noted that such a scanning of the magnetic head 16, which may be the magnetic head 16(n) scanning over the recording surface 26n, is controlled according to a reordering table that describes the seek order of various sectors of various tracks, determined in view of the seek time. Thus, when the content of the reordering table is inappropriate, the magnetic head may reach the target track and the target sector with a wrong timing and has to wait on the target track until the target sector comes to the position ready for reading by the magnetic head.
In the case the seek time in the reordering table is valid, the transition from a first track 30S to a second track 30T on the magnetic recording surface such as the recording surface 26n occurs just in time as represented in FIG. 5A, and the read command 1 specified by the reordering table and commanding the reading of a specified sector of the track 30S by the magnetic head 16(n) and the read command 2 specified also by the reordering table and commanding the reading of a specified sector of the target track 30T by the magnetic head 16(n), are executed consecutively without a waiting time.
In the case the seek time in the reordering table is inappropriate, on the other hand, the heading part of the target sector on the second target track 30T may have passed the location of the corresponding magnetic head 16(n) when the read command 2 is issued as represented in FIG. 5B. In such a case, it is necessary to hold the magnetic head 16(n) on the second target track 30T and wait for a further turn of the magnetic disk 14 until the heading part of the sector on the track 30T comes to the position ready for scanning by the magnetic head 16(n).
In any of these cases explained above, there appears a waiting time and the access speed of the magnetic disk device is deteriorated.
Accordingly, it is a general object of the present invention to provide a novel and useful magnetic disk device and a control process thereof wherein the foregoing problems are eliminated.
Another and more specific object of the present invention is to provide a magnetic disk device having a reduced access time and an access control process that reduces the access time.
Another object of the present invention is to provide a disk storage device storing information on a rotary recording disk, comprising:
a rotary recording disk;
one or more heads each scanning over a corresponding recording surface of said rotary recording disk generally in a radial direction of said rotary recording disk; and
a control circuit controlling a scanning motion of said one or more heads such that said head scans a selected region of a selected track, said control circuit comprising a seek control circuit,
said seek control circuit detecting occurrence of a waiting time in which said head waits on said selected track for a rotation of said rotary disk until said selected region comes to a position ready for scanning by said head, said seek control circuit further causing said head to scan a different part of said rotary disk different from said selected region during said waiting time.
Another object of the present invention is to provide a method of optimizing a seek operation of a disk storage device, comprising the steps of;
causing a seek operation in a first head to scan a first track;
detecting occurrence of a waiting time for said first head on said first track; and
causing a second head, in response to a detection of occurrence of said waiting time, to scan a second track during an interval corresponding to said waiting time.
According to the present invention, the waiting time waiting for the magnetic disk to rotate until the selected sector comes to a position ready for scanning by the magnetic head is utilized for a useful purpose and the problem of occurrence of a loss time during the operation of the magnetic disk device is eliminated.
Another object of the present invention is to provide a disk storage device for storing information on a rotary recording disk, comprising:
a rotary recording disk;
first and second heads each scanning a corresponding recording surface of said rotary recording disk;
a control circuit controlling a scanning motion of said first and second heads such that said first head scans a selected region of a selected track, said control circuit comprising a seek control circuit,
said seek control circuit detecting occurrence of a waiting time in which said first head waits on said selected track for a rotation of said rotary disk until said selected region comes to a position ready for scanning by said first head, and
an optimizing circuit activated in response to occurrence of said waiting time, said optimizing unit driving said second head in response thereto and causing said second head to rewrite information on said second track with a skew, determined with respect to said first track, such that said waiting time vanishes substantially.
Another object of the present invention is to provide a method of optimizing a seek operation of a disk storage device, comprising the steps of;
causing a first head to scan a first track;
causing, after a scanning of said first track by said first head, a seek operation in a second head such that said second head scans a second track;
detecting occurrence of a waiting time for said second head on said second track; and
rewriting said second track by using said second head, in response to a detection of occurrence of said waiting time, with a skew with respect to said first track, said skew being determined so as to eliminate said waiting time substantially.
According to the present invention, the skew between the tracks is optimized in conformity with the actual storage device, and further occurrence of the waiting time is eliminated. Thereby, further occurrence of waiting time is eliminated and the seek speed of the disk device is improved.
Another object of the present invention is to provide a disk storage device for storing information on a rotary recording disk, comprising:
a rotary recording disk;
a head scanning a recording surface of said rotary recording disk;
a control circuit controlling a scanning motion of said head such that said head scans a selected region of a selected track, said control circuit comprising a seek control circuit,
said seek control circuit detecting occurrence of a waiting time in which said head waits on said selected track for a rotation of said rotary disk until said selected region comes to a position ready for scanning by said head, and
an optimizing circuit activated in response to occurrence of said waiting time, said optimizing unit updating a seek time held in an reordering table, said reordering table specifying a seek order based on said seek time.
Another object of the present invention is to provide a method of optimizing a seek operation of a disk storage device, comprising the steps of:
causing a head to scan a first track;
causing, after a scanning of said first track by said head, a seek operation in said head such that said head scans a second track, said seek operation being conducted according to a seek order described in a reordering table, said reordering table including a seek time;
detecting occurrence of a waiting time for said head on said second track; and
rewriting said seek time in said reordering table, in response to a detection of occurrence of said waiting time, such that said waiting time of said head on said second track is vanished.
According to the present invention, the reordering table controlling the seek order based on the seek time of the head across the tracks, is optimized in conformity with the actual state of the disk storage device. Thereby, further occurrence of waiting time is eliminated and the seek speed of the disk device is improved.
Other objects and further features of the present invention will become apparent from the following detailed description when read in conjunction with the attached drawings.